Turning Circle / Advance / Transfer Estimator gives first-pass maneuvering metrics from vessel speed, applied rudder angle, and vessel length when vessel-specific maneuvering curves are unavailable. It estimates turning radius, tactical diameter, advance, transfer, and time to a 90-degree heading change for bridge-team briefings, pilot exchange preparation, simulator discussion, and early maneuver planning. The method is intentionally approximate and cannot represent hull form, loading condition, shallow-water effects, propulsion configuration, windage, or actual rudder response. Use it only as context until pilot-card, wheelhouse poster, sea-trial, simulator, or observed maneuvering data is available.
Enter values in the left panel, keep units explicit, run the calculation, then copy or share the result. Invalid fields are highlighted immediately.
How to use this tool
Enter vessel speed in knots, applied rudder angle in degrees, and vessel length overall in meters.
Run the estimator to compute turning radius, tactical diameter, advance, transfer, and estimated time to 90 degrees.
Compare each output against the vessel pilot card, wheelhouse poster, sea-trial data, simulator data, or recent observed maneuvers.
Use the result for briefing scale and margin discussion, not for final maneuver orders.
Turning Inputs
Result
Turning radius: 178.2 m
Tactical diameter: 356.4 m
Advance: 463.3 m
Transfer: 267.3 m
Estimated time to 90° turn: 45.3 s
Formula or method
The estimator scales turning radius by vessel length, rudder angle, and speed using a simple empirical approximation.
Tactical diameter is estimated as twice the turning radius, advance as 2.6 times radius, and transfer as 1.5 times radius.
Time to 90 degrees uses quarter-circle arc length divided by speed converted to meters per second.
Worked example
Preparing a pilot exchange maneuver brief
Speed: 12 kn
Rudder angle: 20 deg
Length overall: 110 m
Result: The estimator returns first-pass turning radius, tactical diameter, advance, transfer, and time to a 90-degree heading change.
Use the values to frame expected maneuver scale, then replace them with vessel-specific pilot-card or sea-trial figures before relying on the plan.
How to interpret the result
Turning-circle estimates are useful for scale awareness, but actual vessel response can differ sharply from this simplified approximation.
Advance is the approximate distance made in the original direction before the vessel has turned through the reference heading.
Transfer is the approximate sideways displacement from the original track during the turn.
Tactical diameter helps compare whether available water, channel width, traffic, and abort margins are plausible.
Time to 90 degrees is a rough timing cue, not a helm order or guarantee of heading response.
Common mistakes
Treating an empirical estimate as vessel-specific maneuvering data.
Ignoring shallow water, bank effect, wind, current, squat, loading, trim, propulsion mode, or tug assistance.
Comparing estimated transfer or advance with charted limits without adding operational safety margin.
Using speed over ground when the maneuvering reference needs speed through water, or vice versa.
Review note and limitations
Method - empirical first-pass maneuvering approximation from length, rudder angle, and speed.
Does not model hydrodynamics, pivot point movement, stopping distance, tactical diameter asymmetry, shallow-water effects, or propulsion/rudder configuration.
Does not replace pilot-card data, wheelhouse poster data, simulator training, sea trials, or bridge-team procedures.
Navigation planning support only. Do not use this page as a substitute for vessel-specific maneuvering data, pilot guidance, bridge-team procedures, or qualified navigation judgment.
FAQ
Is this the same as a vessel's pilot-card turning data?
No. It is a rough approximation for context. Pilot-card, wheelhouse-poster, sea-trial, simulator, or observed vessel data should take priority.
What are advance and transfer?
Advance is distance made along the original course during the turn. Transfer is sideways displacement from the original track.
Why does shallow water matter?
Shallow water, bank effect, squat, and restricted channels can materially change turning behavior and required margins.
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